Starting with the exchanger you should trade with, I will suggest that you start with the top exchangers like Binance, Bitfinex or OKEx, make your choice from the three or maybe if there is any other you like you can go for that if you think it is better.

And as for tips on how you can trade I will first tell you not to involve your emotions when it comes to trading. Next thing is to never assume that a falling coin is an opportunity, cause sometimes it might take years.